CropsLife cycle, population dynamics
- Form of conservation and alternative hosts
Overwintering females fertilized ensure the restarting of populations at the beginning of spring. Different alternative hosts (wild fruits) allow its presence throughout the year with spawning on winter fruits such as mistletoe (figure 1).
- Stages of development (biological cycle see figure 2)
Females can lay several eggs per day, on different fruits (cherry, mistletoe, cherry laurel, wild blackberry, American grape, hièble elderberry and black elderberry, species present around the vineyard), with a total fertility that can be greater than 400 eggs per female. The eggs are inserted into the bay and it can accommodate several larvae. Thanks to its robust ovipositor, this fly lays on healthy fruit with a thin film, but it can also lay on injured fruit.
On very ripe fruits, after the start of an attack by Drosophila suzukii, larvae of different species of Drosophila may coexist.
- Dispersion in culture
D. suzukii always performs at least one generation per year on the grape during the ripening phase. This Drosophila has the role of a pioneer species, it infests the grape when the other species are not present, that is to say the healthy grape at maturity.
Drosophila suzukii is present in the wine-growing landscape on wild fruits such as elderberries, wild blackberries or mistletoe berries, for example. These hosts are regularly infested each year. The role of this habitat as a source of infestation in vineyard plots is under study.
- Favorable development conditions
Note that the overwintering sites of adults, their survival rate depending on the climate, the identification of areas of primary invasion at the end of winter, the flight distance, the factors of attraction of crops (olfactory, visual ), the influence of the plot environment (ecological diversity ) are parameters that influence the biological cycle of this Drosophila.
As a direct pest, the observed population levels seem unlikely to generate damage. However, the years characterized by a humid climate during veraison, then dry and hot in September, allow an early attack of D. suzukii on the bunch which will be followed by the development of other fruit flies and consequently by acid rot.
Bibliography:
Laveau et al. (2016) Drosophila suzukii in the vineyard: what's new in 2015? Union Girondine des Vins de Bordeaux, 1130, 53-59
Delbac L, et al. (2018) Drosophila suzukii in the Bordeaux vineyards - Status report since its discovery. Union Girondine des Vins de Bordeaux, 1155, 40-42